Vinyl Chloride


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Introduction

At room temperature, vinyl chloride is a flammable, colorless gas with a sweet smell. Under pressure or at low temperatures, it is a liquid.

Vinyl chloride does not occur in nature, though it is sometimes a byproduct of the anaerobic dechlorination of tetrachloroethene or trichloroethene by certain subsurface microorganisms. Rather, it is a major It is a Production of vinyl chloride in the United States grew at an average rate of about 7% from the early 1980s to the early 1990s, with current growth at about 3% annually. Most of the vinyl chloride produced in the United States is used to make a polymer called polyvinyl chloride (PVC), which consists of long repeating units of vinyl chloride. PVC is used to make a variety of plastic products including pipes, wire and cable coatings, and packaging materials. Other uses include furniture and automobile upholstery, wall coverings, housewares, and automotive parts. At one time, vinyl chloride was used as a coolant, as a propellant in spray cans, and in some cosmetics. However, since the mid-1970s, vinyl chloride mostly has been used in the manufacture of PVC. Other names for vinyl chloride include chloroethene, chloroethylene, ethylene monochloride, and monochloroethylene.

Structural diagram: National Institutes of Health


Fate & Transport

Most of the vinyl chloride that enters the environment comes from vinyl chloride manufacturing or processing plants, which release it into the air or into waste water. EPA limits the amount that industries can release. Vinyl chloride also is a breakdown product of other synthetic chemicals. Vinyl chloride has entered the environment at hazardous waste sites as a result of improper disposal or leakage from storage containers or spills, but some may result from the breakdown of other chemicals. In addition, vinyl chloride has been found in tobacco smoke at very low levels.

Liquid vinyl chloride evaporates easily. Vinyl chloride in water or soil evaporates rapidly if it is near the surface. Vinyl chloride in the air breaks down in a few days, resulting in the formation of several other chemicals including hydrochloric acid, formaldehyde, and carbon dioxide.

Some vinyl chloride can dissolve in water. Vinyl chloride can migrate to groundwater and can be in groundwater due to the breakdown of other chemicals. Vinyl chloride is unlikely to build up in plants or animals that you might eat.

Exposure Pathways

Because vinyl chloride usually exists in a gaseous state, you are most likely to be exposed to it by breathing it. Vinyl chloride is not normally found in urban, suburban, or rural air in amounts that are detectable by the usual methods of analysis. However, vinyl chloride has been found in the air near vinyl chloride manufacturing and processing plants, hazardous waste sites, and landfills. The amount of vinyl chloride in the air near these places ranges from trace amounts to over 1 ppm. Levels as high as 44 ppm were found in the air at some landfills. You can also be exposed to vinyl chloride in the air through tobacco smoke from cigarettes or cigars (both active smoking and second-hand smoke). Levels of vinyl chloride in tobacco smoke are very low, usually around 530 nanograms per cigarette (a nanogram is 0.000000001 gram).

You can be exposed to vinyl chloride by drinking water from contaminated wells. Most drinking water supplies do not contain vinyl chloride. In a 1982 survey, vinyl chloride was found in fewer than 1% of the 945 groundwater supplies tested in the United States. The concentrations in groundwater were up to 0.008 ppm. Other studies have reported vinyl chloride in groundwater at concentrations at or below 0.38 ppm. At one time, the flow of water through PVC pipes added very low amounts of vinyl chloride to water. For example, in one study of newly installed pipes, the drinking water had 0.001 ppm of vinyl chloride. No current information is available about the amount of vinyl chloride released from PVC pipes into water. In the past, vinyl chloride could get into food stored in materials containing PVC, but the U.S. government now regulates the amount of vinyl chloride in food packaging materials. When less than about 1 ppm of vinyl chloride is trapped in PVC packaging, vinyl chloride in detectable amounts does not enter food by contact with these products.

People who work at facilities that make vinyl chloride or PVC usually are exposed to higher levels than the general population. Work exposure occurs primarily from breathing air that contains vinyl chloride, but workers also are exposed when vinyl chloride contacts the skin or eyes. Based on studies using animals, it is possible that if vinyl chloride comes into contact with your skin or eyes, extremely small amounts could enter your body.

Metabolism

If vinyl chloride gas contacts your skin, tiny amounts may pass through the skin and enter your body. Vinyl chloride is more likely to enter your body when you breathe air or drink water containing it. This could occur near certain factories or hazardous waste sites or in the workplace. At low levels (<20 ppm), most of the vinyl chloride that you breathe or swallow enters your blood rapidly, then travels throughout your body. When some portion of it reaches your liver, your liver changes it into several substances. Most of these new substances also travel in your blood; once they reach your kidneys, they leave your body in your urine. Most of the vinyl chloride is gone from your body a day after you breathe or swallow it. The liver, however, makes some new substances that do not leave your body as rapidly. A few of these new substances are more harmful than vinyl chloride because they react with chemicals inside your body and interfere with the way your body normally uses or responds to these chemicals. Some of these substances react in the liver and, depending on how much vinyl chloride you breathe in, may produce damage there. Your body needs more time to get rid of these changed chemicals, but eventually removes them as well. If you breathe or swallow more vinyl chloride than your liver can chemically change, you will breathe out excess vinyl chloride.

Health Effects

If you breathe high levels of vinyl chloride, you will feel dizzy or sleepy. These effects occur within 5 minutes if you are exposed to about 10,000 ppm of vinyl chloride. You can easily smell vinyl chloride at this concentration. It has a mild, sweet odor. If you breathe still higher levels (25,000 ppm), you may pass out. You can rapidly recover from these effects if you breathe fresh air. Some people get a headache when they breathe fresh air immediately after breathing very high levels of vinyl chloride. People who breathe extremely high levels of vinyl chloride can die. Studies in animals show that extremely high levels of vinyl chloride can damage the liver, lungs, and kidneys. These levels also can damage the heart and prevent blood clotting. The effects of ingesting vinyl chloride are unknown. If you spill liquid vinyl chloride on your skin, it will numb the skin and produce redness and blisters.

Some people who have breathed vinyl chloride for several years have changes in the structure of their livers. People are more likely to develop these changes if they breathe high levels of vinyl chloride. Some people who have worked with vinyl chloride have nerve damage, and others develop an immune reaction. The lowest levels that produce liver changes, nerve damage, and immune reaction in people are not known. Certain jobs related to PVC production expose workers to very high levels of vinyl chloride (i.e., pools of liquid vinyl chloride in vats or autoclaves). Some of these workers have problems with the blood flow in their hands. Their fingers turn white and hurt when they go into the cold and may take a long time to recover when they go into a warm place. In some of these people, changes have appeared on the skin of their hands and forearms. Also, bones at the tips of their fingers have broken down. Studies suggest that some people may be more sensitive to these effects than others.

Some men who work with vinyl chloride have complained of a lack of sex drive. Studies in animals showed that long-term exposure can damage the sperm and testes. Some women who work with vinyl chloride have reported irregular menstrual periods. Some have developed high blood pressure during pregnancy.

Results from several studies have suggested that breathing air or drinking water containing moderate levels (100 ppm) of vinyl chloride might increase their risk for cancer. However, the levels used in these studies were much higher than levels found in the ambient air and/or most drinking water supplies. Studies of workers who have breathed vinyl chloride over many years showed an increased risk for cancer of the liver. Brain cancer, lung cancer, and some cancers of the blood also may be connected with breathing vinyl chloride over long periods. Studies of long-term exposure in animals showed that cancer of the liver and mammary gland may increase at very low levels of vinyl chloride in the air (50 ppm). Lab animals fed low levels of vinyl chloride each day (2 mg/kg/day) during their lifetime had an increased risk of getting liver cancer.

The U.S. Department of Health and Human Services has determined that vinyl chloride is a known carcinogen. The International Agency for Research on Cancer has determined that vinyl chloride is carcinogenic to people, and EPA has determined that vinyl chloride is a human carcinogen.

Information excerpted from:

Toxicological Profile for Vinyl Chloride 2006 Update

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services